Well, JBoss automatically ships with the Hypersonic database to give you features requiring persistence out of the box...like JMS. But even if you use the Hypersonic DB, you still need to: * Create a database (namespace, not database server) for your application (See references for your DB impl). * Create your DB schema to match that which JPA/EJB3 Entities expect. See hbm2ddl configuration for Hibernate, can be done from persistence.xml; this will handle this step for you via autogen to save you this step and keep everything in line during development. * Create a datasource to define the connection pool to your DB. If you use Hypersonic built-in, this is already done. Otherwise you must make your own *-ds.xml file and place in "deploy". http://wiki.jboss.org/wiki/Wiki.jsp?page=DSdotXML * Create a persistence.xml to define your persistence unit (this will point to your datasource); yes this is where implementation-specific config may be done (ie. Hibernate in JBoss's case) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4134690#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...